One of the most strikingly coloured nemertean species in the North Sea: vivid brick red, orange-red, garnet-red or brownish red marked with three white longitudinal stripes and about 50 transverse rings. The mid-dorsal stripe anteriorly extends to the distinctive rounded cephalic lobe, which is the same colour as the remainder of the body, and terminates at a transverse white headband bordering the pigmented tip of the snout. The two lateral stripes, in contrast, do not reach the head and run posteriorly from the first white ring encircling the body. Apart from the first two or three, the rings are arranged more or less equidistantly. The ventral surface is paler than the dorsal one (T. annulatus).
The species attains a length of 75 cm or more but rarely exceeds 3-4 mm width unless it is strongly contracted.
The body wall inner circular muscle layer is well developed; no dorsal body wall muscle cross. The cephalic glands are well developed. Lateral sensory organs are absent.
In the British Isles, it reproduces during the months of June and July.
Although sometimes found intertidally beneath stones, among Laminaria roots or on sand or mud near the low water level, it is more common sublittorally on a wide variety of substrata (gravel, stones, mud, fine sand, sand mixed with shell fragments and among scallops) at depths to 40 m or deeper. It readily secretes a silken mucous tube to which sediment particles adhere.
It has a wide geographic range in the northern hemisphere, from the Pacific coast of North America eastwards to the Atlantic, North Sea and Mediterranean coasts of Europe. The internal morphology of Tubulanus annulatus apparently varies with its geographic distribution.